It is now up to the Constitutional Court.

Following the National Assembly’s approval of the impeachment motion against President Yoon Suk Yeol on Saturday, his presidential powers were suspended immediately.

Prime Minister Han Duck-soo is now in charge as acting president of South Korea, although he is similarly facing investigation for his alleged role and participation in a Cabinet meeting held shortly before Yoon's imposition of martial law on Dec. 3.

The Constitutional Court must now deliberate on the case to decide whether to uphold or dismiss the parliamentary impeachment. Under the Constitutional Court Act, the court has 180 days to deliver its ruling.

Given the gravity of the case, the presidential impeachment trial is a top priority for the court, which will aim for a resolution as swiftly as possible.

South Korea has previously experienced two presidential impeachment trials, for Presidents Roh Moo-hyun and Park Geun-hye.

Roh’s trial in 2004 lasted 63 days, while Park Geun-hye's in 2017 concluded in 91 days. The court’s verdicts differed in the two cases: It dismissed Roh’s case, allowing him to resume his duties, while it unanimously upheld Park’s impeachment, removing her from office.

The impeachment trial of Yoon will begin once the National Assembly formally presents its resolution. The case will then be heard by the court’s full bench, with all justices participating.

Yoon is expected to form a team of legal representatives to defend himself, while the parliament will also forge its “prosecutor” team, possibly led by Legislation and Judiciary Committee Chair Rep. Jung Chung-rae.

Attendance by the accused is not mandatory, a precedent set during impeachment trials for former Presidents Roh and Park, both of whom opted not to appear.

Court faces challenges with six justices

The impeachment trial comes amid concerns about the Constitutional Court’s ability to deliver a timely and legitimate ruling with just six justices. Three seats have been vacant since October, leaving the court short of its full nine-member complement.

According to constitutional law, a minimum of six votes is required to decide an impeachment case and at least seven justices must be present for the review to proceed. However, the court temporarily suspended enforcement of this rule to prevent judicial paralysis.

The adjustment means decisions can only be made unanimously under the current six-member system, increasing the difficulty of reaching a verdict in a politically charged case such as presidential impeachment.

The situation has prompted calls for swift action from the ruling and opposition parties to fill the vacant seats. The National Assembly would need to recommend candidates and the acting president would appoint the justices.

Acting presidents have previously appointed Constitutional Court justices in impeachment situations. For example, during Park’s impeachment trial, acting President Hwang Kyo-ahn appointed Justice Lee Seon-ae to the bench.

If the Constitutional Court dismisses the impeachment, Yoon will return to office immediately.

However, if the court upholds the impeachment, a presidential election must be held within 60 days. In Park’s case, her impeachment was upheld on March 10, 2017, and Moon Jae-in was elected president on May 9.